Initially, I just wanted this tool to analyse the compatibility of a chrome extension with the current implementation state of WebExtensions (analysing both chrome api calls in code and manifest.json entries). I ended up adding a conversion capability that repackages the chrome extension so it can be directly loaded on Firefox, and packages it with some code that proxies the global chrome object, so devs get warnings on the console instead of exceptions whenever an unsupported api call is done.

I’m one of the developers working on the new addons-linter for new add-ons (eg. Web Extensions in Firefox). We were just saying last week that this would be an awesome feature to integrate into the new add-on linter/validator.